Wrapper to bridge realms auto updating behaviour with SwiftUIs value based immutability requirement. (Extract from https://stackoverflow.com/questions/57160790/index-out-of-bounds-when-using-realm-with-swiftui)

ListKey.swift

import RealmSwift

typealias Model = Object & Identifiable

struct ListKey<T: Model>: Identifiable {
    let id: T.ID
}

extension Results where Element: Model {
    
    subscript(key: ListKey<Element>) -> Element? {
        Element.primaryKey().flatMap { self.filter("\($0) = %@", key.id).first }
    }
    
    var keyedEnumeration: [ListKey<Element>] {
        guard let key = Element.primaryKey() else { return [] }
        let keys = value(forKey: key) as! [Element.ID]
        return keys.enumerated().map { ListKey(id: $0.1) }
    }
}

@duncangroenewald that is because RealmSwift.List s value(forKey: key) is different from the Results s. It returns [AnyObject] instead of Any.

let keys: [AnyObject] = value(forKey: key) compiles but it requires a cast to occur later in return keys.enumerated().map { ListKey(id: $0.1) } like

        return keys.enumerated().map { ListKey(id: $0.1 as! Element.ID) }

I have not tried whether it works or not. I suppose the key is usually a String or Int, and none of them conforms to AnyObject so this might crash.

An other hacky solution, to convert the List to Results with a simple filtering. As far as I know realm handles this very well, so not much performance is lost.

    var keyedEnumeration: [ListKey<Element>] {
        guard let key = Element.primaryKey() else { return [] }
        let keys = filter("TRUEPREDICATE").value(forKey: key) as! [Element.ID]
        return keys.enumerated().map { ListKey(id: $0.1) }
    }